Use of hair dyes and other personal-appearance products has a major public health impact worldwide, particularly among women. In most countries, the hairdressing profession, including exposures, process, and protection, is unregulated and employment data is limited. In addition to occupational exposure, the general population is exposed to these chemicals as clients of beauty salons, consumers of commercially available chemicals for home use, and through water that enters the waste stream from these processes. Recently, more young women are using these services, leading to more frequent exposure to these chemicals at a younger age. Consequently, all over the world, hairdressing professionals are frequently exposed to many risk factors for occupational diseases such as asthma and other respiratory disorders, contact dermatitis, poor work posture, repetitive work tasks, adverse reproductive outcomes, and cancer. Despite the large population at risk, specific compounds associated with cancer and reproductive health effects have not been elucidated, and no prospective cohort studies using individual exposure measurements of specific hairdressing chemicals have been performed to date. The aim of this study is to more fully characterize chemical exposures in hairdresser populations in Brazil and the United States and to investigate the health effects associated with these chemicals. More clearly defining phenotypic outcomes will allow for further studies to characterize risk alleles in this population. Ultimately, understanding these risks could lead to improved protection for hairdressers and consumers of these services, as well as better understanding of the effects of chronic, low level chemical exposure in the global environment on human health. PUBLIC HEALTH RELEVANCE: All over the world, hairdressing professionals, typically women are frequently exposed to many risk factors for occupational diseases such as asthma and other respiratory disorders, contact dermatitis, poor work posture, repetitive work tasks, adverse reproductive outcomes, and cancer. Despite the large population at risk, specific compounds associated with health effects have not been determined. Ultimately, understanding these risks could lead to improved protection for hairdressers and consumers of these services, as well as better understanding of the effects of chronic, low level chemical exposure in the global environment on human health.